Field of the Invention
The present invention relates to an apparatus and method which supply a piston when assembling it in the cylinder block of an engine.
Description of the Related Art
It is necessary to insert a piston into the cylinder bore formed in a cylinder block upon diameter reduction of a piston ring. Under the circumstance, there has been proposed a method of inserting a piston into a cylinder bore by pushing the piston out of a dedicated guide tube upon temporarily inserting the piston into the guide tube while the diameter of a piston ring is reduced (Japanese Patent Laid-Open No. 2003-266255).
When inserting a piston into a cylinder bore, in order to prevent the cylinder bore and a connecting rod from interfering with each other, a cylinder block is set to make the cylinder bore face vertically, and the piston is set in a guide tube so as to make the connecting rode face vertically. For this reason, a piston gripping robot designed to insert a piston into a guide tube grips the outer surface of the piston while the top portion of the piston faces upward and then inserts the piston into the guide tube.
Depending on the arrangement of an automatic assembly system, a piston with a connecting rod before insertion into a cylinder bore is sometimes prepared by being mounted on a pallet while the top portion of the piston faces downward depending on procedures for a series of assembly operations for the piston and the connecting rod. When automating a series of operations from assembly operations for a piston and a connecting rod to the operation of inserting the piston into a cylinder bore, it is necessary to transfer the piston to a piston gripping robot upon reversing the posture of the piston from a downward state to an upward state.
As a procedure for transferring a piston to a piston gripping robot upon reversing the posture of the piston, the following procedure may be used: making a posture reversing robot pick up a piston from a pallet or the like, revere the posture of the piston, and mount the piston on the pallet or the like, and making the piston gripping robot pick up the piston. This procedure, however, requires a tact time when mounting a piston on a pallet or the like. The tact time can be shortened if it is possible to make the posture reversing robot directly transfer a piston to the piston gripping robot in air upon reversing the posture of the piston.
However, since the piston gripping robot needs to grip the outer surface of a piston, the posture reversing robot reverses the posture of the piston upon gripping the connecting rod. The centrifugal force generated at the time of reversing may shift the gripping position of the posture reversing robot. As a consequence, the posture of the piston may shift relative to the connecting rod. Transferring the piston to the piston gripping robot in air in this state will degrade the accuracy of piston gripping.